1. A conventional telephone line with 3 kHz bandwidth and having 30 dB signal-to-noise ratios can carry information at a rate of
- 15 kbps
- 30 kbps
- 16 Mbps
- 3 kbps
2. If the probability of a message is 1/4, then the information in bits is
- 1 bit
- 2 bit
- 4 bit
- 8 bit
3. Digital modulation techniques are used in a satellite communication system, because
- they are easier to handle
- large bandwidth utilization is possible
- they have a spectral efficiency
- they are less prone to interference
4. A TDM link has 20 signal channels and each channel is sampled at 8 kHz. Each sample is represented by 7 bits and contains an additional bit for synchronization. The total bit rate for the TDM link is
- 1180 kbps
- 1128 kbps
- 128 Mbps
- 1280 kbps
5. Frequency frogging is used in the carrier system to
- Conserve frequencies
- Reduce distortion
- Reduce cross talk
- Reduce bandwidth
6. Digital modulating system among the following is
7. A binary data is to be sent at the rate of 100 kbps over a channel with 60 dB transmission loss and noise power spectral density No = 10-12 W/Hz at the receiver. The digital modulation system that will require minimal transmitted power if the probability of error is to be maintained at 10-3 is
- Non-coherent ASK
- Coherent BFSK
- 16-array PSK
8. MSK (Minimum Shift Keying) is an orthogonal FSK scheme that gets its name from the fact that
- the phase shift is minimum.
- the error probability is minimum.
- the transmission power required is minimum.
- the transmission bandwidth required is minimum.
9. Which one of the following statements is incorrect about the matched filter?
- The maximum output SNR depends on the input signal energy
- The impulse response is reversed delayed version of the input signal
- The error probability depends on the wave shape of the signal
- Matched filter and correlator gives identical reception performances.
10. A digital communication system uses 8-PSK modulation and transmits 3600 bps. What is the symbol rate?
- 10800 symbols/sec
- 450 symbols/sec
- 28800 symbols/sec
- 1200 symbols/sec
11. Which signalling scheme is most affected by noise?
12. In the case of data transmission, which one of the following systems will give the maximum probability of error?
13. Which one of the following statements is correct?
For coherent detection of digital signals, the receiver must be
- synchronized in time only
- synchronized in phase only
- unsynchronized in time and phase
14. A modulation technique in which bandwidth of the modulated signal is extended well beyond the bandwidth of the modulating signal, independent of the modulating signal bandwidth, is called
- Wide-band modulation
- Extended bandwidth modulation
- Spread spectrum modulation
- Narrow-band modulation